Blood vessel catheter and injection system for carrying out a blood pressure measurement of a patient

ABSTRACT

An injection system for injecting an injectate fluid into a blood vessel of the patient and for carrying out a blood pressure measurement of a patient. The injection system includes a catheter tube having a first end for penetrating the blood vessel of the patient, and a pressure sensor which is arranged close to a second end of the catheter tube and can sense a pressure of a liquid in the catheter tube as an indication of the blood pressure of the patient.

The present application is a continuation of U.S. patent applicationSer. No. 11/637,546, filed Dec. 12, 2006 now abandoned entitled BloodVessel Catheter and Injection System for Carrying Out a Blood PressureMeasurement of a Patient. It also claims priority to German applicationDE 10 2005 060079.4, filed Dec. 15, 2005, entitled Blood Vessel Catheterand Injection System for Carrying Out a Blood Pressure Measurement of aPatient, the entire disclosures of which are incorporated by referenceherein.

The present invention relates to blood vessel catheter located proximateto a patient's body for measuring blood pressure, drawing blood samplesor injecting fluids into a blood vessel of the patient. The presentinvention further relates to a system for drawing blood samples orinjecting fluids into the blood vessel of the patient and for carryingout a blood pressure measurement of a patient.

BACKGROUND

Measurement systems for measuring blood pressure of a patient's body arewell known in clinical appliances. They usually comprise a rinsing fluidreservoir which is connected using a fluid flow tube to a catheter tube,which in use penetrates a patient's body such that the rinsing fluid issupplied as a continuous rinsing fluid stream. Along the rinsing channelone or more valves can be arranged to manually stop the rinsing of thefluid into the patient's body.

The continuous measurement of a blood pressure of a patient is importantto monitor the condition of ill patients. It is common that themeasurement of the blood pressure is carried out using a single usepressure sensor and a rinsing system both mounted on an organizer plate.This organizer plate with the sensors is well accessible on heart levelfor the operator. The pressure sensor on this organizer plate is thenconnected to the patient via a long tube which is filled with liquid.Thus, the pressure signal is hydraulically transmitted via the transfertube. Typically there is a 3 way stop cock between patient and pressuresensor for drawing blood samples Or injecting fluids.

The disadvantage of this system is that the pressure signal is falsifiedby the transfer characteristic of the long transfer tube system due todamping or resonance as a result of the length of the transfer tube.

As another possibility for measuring the blood pressure the use of a tipmanometer is known. The tip manometer is located at the tip of thecatheter tube such that in use the manometer is located inside thepatient's body. Although such an arrangement provides a very good signaltransmission it is very expensive and a larger diameter of the cathetertube is needed. Furthermore, controlling and adjusting the zero pointpressure of the tip manometer is no longer possible after the cathetertube is placed inside the patient's body.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a blood vessel catheterand a fluid transfer system which avoids the drawbacks of the prior artand allows for an accurate and continuous measurement of the bloodpressure of the patient.

The present invention provides a blood vessel catheter and a fluidtransfer system.

According to a first aspect of the present invention, a blood vesselcatheter is provided for locating in close proximity to a patient's bodyand for injecting an injectate fluid into a blood vessel of the patientor drawing blood samples from the patient. The blood vessel catheterincludes a catheter tube having a first end for penetrating the bloodvessel of the patient and a pressure sensor which is arranged at asecond end of the catheter tube outside of the patient, wherein thepressure sensor is adapted to sense a pressure of the liquid in thecatheter tube as an indication of the blood pressure of a patient.

The catheter has an advantage that the pressure sensor for sensing theblood pressure of the patient is located close to the blood vessel ofthe patient such that a damping or a resonance of the detected pressureis reduced or eliminated. Furthermore, the pressure sensor is locatedoutside of the patient's body such that a zeroing of the pressure sensorcan be carried out even if the catheter is in use.

Preferably, the pressure sensor is further adapted to supply an electricpressure signal, wherein an electric interface is provided to releasablycouple the pressure sensor to a reusable measurement unit. Thereby, thecatheter is provided as a disposable item which can be further coupledto a disposable fluid transfer unit.

According to another embodiment of the present invention, a valve,especially a control valve, is provided which is arranged between theend of the catheter tube and the pressure sensor wherein the valve isadapted to be operated depending on a valve activation signal. A valvecontrol interface may be provided to couple the valve with a remotevalve control element.

Advantageously, the valve includes a squeezable tube portion having anadaptable lumen wherein the squeezable tube is provided in such a way toadapt the size of the lumen depending on a pneumatic or hydraulic valveactivation signal.

According to a further embodiment, the valve may be coupled to theelectric interface for receiving an electric valve activation signal.

Preferably, a connector is provided for coupling the catheter tube to aunit for rinsing, injection or drawing blood samples. This allows forthe catheter to be provided as a disposable item which can be releasablycoupled to a fluid transfer unit. Unlike the previous art this connectoris close to the patient and preferably arranged upstream to the pressuresensor

The present invention may further provide a shut-off valve arrangedupstream to the pressure sensor which is adapted to be manually operatedfor controlling a liquid flow through the catheter tube. This allows aninstant manual control of the fluid flow into the patient's body. Forthis valve also a 3 way stop cock could be used. This can allowconvenient application of a guide wire to the catheter e.g. for aSeldinger catheter placement technique.

According to another aspect of the present invention a fluid transfersystem is provided for rinsing the catheter or injecting an injectatefluid into a blood vessel of the patient or drawing blood samples fromthe patient and for carrying out a blood pressure measurement on apatient. The fluid transfer system includes a catheter tube having afirst end for penetrating the blood vessel of a patient and a pressuresensor which is arranged close to a second end of the catheter tube,wherein the pressure sensor is adapted to sense a pressure of liquid inthe catheter tube as an indication of the blood pressure of the patient.

The fluid transfer system according to present invention allows acontinuous measurement of a blood pressure of a patient while the bloodpressure is sensed close to the patient's body. A damping or a resonanceof the pressure signal thus advantageously can be avoided.

According to an embodiment of the present invention, a measurement unitis provided which is electrically coupled to the pressure sensor fordetermining a pressure value.

Preferably, a control valve is arranged between the end of the cathetertube and the pressure sensor, wherein the control valve is adapted to beoperated depending on a valve activation signal. Furthermore, the fluidtransfer system includes a remote valve control element for providingthe valve activation signal. The valve permits remote control of thefluid flow through the catheter tube.

Advantageously, a pneumatic signal activation line is provided to couplethe valve to the valve control element wherein the remote valve controlelement provides a pneumatic or hydraulic valve activation signal.

Furthermore, it may be provided that the control valve includes asqueezable tube portion having a flexible lumen wherein the squeezabletube is provided in such a way to adapt the flexible lumen depending onthe pneumatic or hydraulic valve activation signal.

According to a preferred embodiment of the present invention the fluidtransfer system includes a reservoir for a rinsing medium, a fluid flowmeans coupled to the catheter tube, and a stop cock which is adapted tocouple the reservoir to the catheter tube in a rinsing position.

Furthermore, the stop cock may be adapted to couple a reference pressureto the fluid flow means in a nulling position.

Moreover, the stop cock may be coupled to the valve control element insuch a way that in the nulling position the valve is closed.

Preferably, the stop cock is adapted to cut off the fluid flow in thefluid flow means in a sampling position.

A fluid transfer system can be provided with a flow control unit havingan upstream end which is coupled to a stop cock and a downstream end.The flow control unit includes a rinsing capillary for providing apredetermined flow of liquid through the fluid flow means, a first checkvalve adapted to open if a pressure difference between the upstream endand the downstream end of the flow control unit exceeds a predeterminedfirst pressure value, and a second check valve adapted to open if apressure difference between the downstream end and the upstream end ofthe flow control unit exceeds a predetermined second pressure value.Preferably the check valves are arranged in order that all fluid pathsare reached by the rinsing streams through the capillary or thedownstream check valve. In case the pressure sensor could not withstandthe pressure generated during manual injection, the smallest crosssection of the fluid path in the flow control unit is chosen smallerthan the smallest cross section downstream the pressure sensor. Thiswill reduce the pressure acting at the sensor position. Alternativelyother pressure limiting means could be applied.

According to a preferred embodiment, a syringe is provided which isconnected to the fluid flow means between the stop cock and the flowcontrol unit for supply a bolus into the fluid flow means, e.g. forflush rinsing. Similar to state of the art blood sampling systems whichare applied before the pressure sensor, blood samples could be drawnthrough the pressure sensor e.g. by:

-   -   Positioning the stopcock in sampling position.    -   Pulling the piston out of the syringe thereby removing rinsing        fluid from the downstream fluid system.    -   Applying a needleless vacuum blood collection system to a blood        sampling port, thereby drawing blood from the patient.    -   Removing the needleless vacuum blood collection system.    -   Pushing back the piston to the syringe, thereby refilling the        rinsing fluid and cleaning the system.    -   Positioning the stopcock in rinsing position.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the present invention are now described in moredetail with respect to the accompanying drawings in which:

FIG. 1 is a schematic view of one embodiment of a fluid transfer systemaccording to the present invention;

FIG. 2 is a more detailed schematic view of a fluid transfer systemaccording to the present invention;

FIG. 3 a-d show a cross-sectional view of a flow control unit arrangedin the fluid flow path of the fluid transfer system according to apreferred embodiment; and

FIG. 3 e-f show a cross-sectional view of a flow control unit arrangedin the fluid flow path of the fluid transfer system according to aanother preferred embodiment; and

FIGS. 4 a and 4 b show a cross sectional view of another embodiment of aflow control unit for use in the fluid transfer system according to thepresent invention in a first and a second operational condition.

FIG. 5 is a schematic view of another embodiment of the fluid transfersystem according to the present invention;

FIG. 6 is a schematic view of another embodiment of the fluid transfersystem according to the present invention;

FIG. 7 is a more detailed schematic view of another fluid transfersystem according to the present invention;

FIGS. 8 a and 8 b are a cross-sectional view from two sides of acatheter as shown in FIG. 7; and

FIG. 9 is a more detailed view of the interface as shown in FIG. 7.

DETAILED DESCRIPTION

FIG. 1 shows a schematic view of a fluid transfer system for supplyingan injected fluid into a patient's body. The fluid transfer systemincludes a blood vessel catheter unit 1, a fluid transfer unit 2, anoperational unit 3, and a reservoir 4 for supplying a rinsing fluid. Theblood vessel catheter unit 1 and the fluid transfer unit 2 may becoupled by a first interface 15 and the blood vessel catheter unit andthe operational unit 3 are coupled by a second interface 19.Furthermore, the fluid transfer unit 2 may include a third interface 29for coupling with the reservoir 4.

The blood vessel catheter unit 1 includes a catheter tube 11 having atip end for penetrating a blood vessel of the patient's body. At anotherend of the catheter tube 11 a control valve 12 is arranged to cut offthe flow of the injected fluid through the catheter tube 11 depending onan activation signal. The activation signal can be applied as apneumatic, hydraulic or electrical signal. In the illustrated embodimentthe activation signal is supplied to the control valve by means of apneumatic valve activation line 19 which is coupled by means of thesecond interface 19 with a valve control element 31. The valve controlelement 31 can be designed as a bellow to provide a pressure forcontrolling the control valve.

The catheter tube 11 can be provided with a temperature sensor 10.Temperature sensor signal lines 16 are coupled to the second interface19. The operational unit 3 which may be coupled to the second interface19 is designed for measuring the temperature. The temperature sensor 10is preferably located at a portion of the catheter tube 11, e.g. thetip, which is located inside the patient's body while in use.

Upstream to the control valve 12 a pressure sensor 13 is coupled to thelumen of the fluid channel within the catheter unit 1. The pressuresensor 13 supplies an electrical pressure signal via electrical pressuresignal lines 17 to the second interface 19 such that the electricpressure signal can be received by the operational unit 3 for detection.The pressure sensor 13 determines the pressure of the liquid within thelumen of the fluid channel as an indication of the blood pressure of thepatient. Usually, the pressure of the liquid in the fluid channelsubstantially corresponds to the blood pressure of the patient. Thus,the second interface 19 includes ports for connecting the temperaturesignal lines 16, the pressure signal lines 17 as well as the pneumaticvalve activation line 18.

The blood vessel catheter unit 1 may further comprise a cut-off valve 14for manually cutting off the fluid stream through the catheter tube 11.

Upstream to the cut-off valve 14, the first interface 15 is locatedwhich is provided as a connector 15. The connector 15 serves for areleasably coupling the fluid transfer unit 2 to the blood vesselcatheter unit 1 such that the rinsing fluid can flow from the fluidtransfer unit 2 to the catheter unit 1. By providing the secondinterface 19 and the connector 15, the blood vessel catheter unit 1 canbe completely released from the operational unit 3 and the fluidtransfer unit 2. This allows that the catheter unit 1 and the fluidtransfer unit 2 can be designed as a disposable item while theoperational unit 3 may e.g. be designed for repeated use.

The fluid transfer unit 2 includes a fluid flow means or section 24 onwhich from upstream to downstream a stop cock 28, a syringe 27, a bloodsample port 26, and a flow control unit 20 are arranged. On the upstreamend of the fluid flow means 24 as the third interface a reservoirconnector port 29 is provided which serves for applying the reservoir 4including the rinsing fluid to be supplied to the patient.

The stop cock 28 can be placed into three positions:

In a first rinsing position the reservoir 4 is connected to the fluidflow means 24 such that the injectate fluid flows via the fluid flowmeans and the connector 15 to the blood vessel catheter unit 1 to supplythe injectate fluid to the patient.

In a nulling position the stop cock 28 applies on the fluid in the fluidflow means 24 a predetermined pressure reference, preferably anatmospheric pressure of an outer environment. Via the fluid flow means24 the predetermined pressure reference is applied to the catheter unit1. Therein, the predetermined pressure reference is used to calibratethe pressure sensor 13.

In a sampling position the stop cock 28 is closed to cut off the fluidflow means 24 from the reservoir 4 as well as from the pressurereference. This position may be used to draw a blood sample via theblood sample port 26. The syringe 27 could be used to remove the rinsingfluid from the catheter unit 1 and the fluid transfer unit 2 and releaseit back after the blood sample is drawn. In the sampling position alsofor flush rinsing a bolus can be applied to the patient using thesyringe 27.

To apply the pressure reference onto the pressure sensor 13 of thecatheter unit 1 it is necessary that the control valve 12 is closed suchthat no fluid can flow through the catheter tube 11. This is achieved byapplying the activation signal on the pneumatic valve activation line18. Furthermore, a calibration signal can be generated by the stop cock28 which is applied to the operation unit 3 such that a calibrationmeasurement of the pressure in the catheter unit 1 can be initiatedautomatically.

The flow control unit 20 is designed to permanently allow a rinsingfluid flow though a capillary 21 which has a predetermined flow ratee.g. of 3 ml/h. To allow that the rinsing fluid could be removed andblood samples could be taken via the connector 15 the flow control unit20 has to provide a bypass which is formed by a first check valve 23.The first check valve 23 opens if a pressure between a downstream end,e.g. at the connector 15, and an upstream end excites a predeterminedfirst threshold pressure. This threshold is chosen at a low negativevalue e.g. 10 mmHg in order not to damage blood cells. The pressuredifference can for example be achieved by the syringe 27 or byconnecting a syringe 26 to the blood sample port 26 and by applying anunderpressure onto the fluid flow means 24. The flow control unit 20includes a second check valve 22 which opens if at least a secondthreshold pressure is applied from upstream to downstream for example ifa bolus is injected into the fluid flow means 24 which shall bedispensed to the patient. This threshold is chosen at a positive valuegreater than the pressure usually applied to the fluid reservoir 4 e.g.500 mmHg.

In FIG. 2 a more detailed view of the fluid transfer system isillustrated. With regard to the blood vessel catheter unit 1 it is shownthat the catheter unit 1 is integrally formed as the interface 19, theconnector 15 and the pneumatic valve activation line 18 which arereleasably connectable to the fluid transfer unit 2 and the operationunit 3.

In the detailed view, it can be seen that the control valve 12 of thecatheter unit 1 is designed as a squeeze valve which can be controlledby means of a pneumatic activation signal that is applied onto aflexible tube 32. An increasing pressure within the pneumatic signalactivation line 18 results in that the lumen of the flexible tube 32 isreduced and finally cut off such that a main flow path 33 within thecontrol valve 12 is closed. By releasing the overpressure within thepneumatic signal activation line 18 the blood pressure of the patientwithin the main flow path 33 results in that the flexible tube 32 openssuch that the rinsing fluid is able to flow again through the cathetertube 11 into the patients body. In a preferred embodiment of the presentinvention, a low or even negative pressure gradient is applied to thepneumatic signal activation line 18 in order to force the flexible tube32 to be extended and forced at the inner wall of the main flow path 33.Thus, it is ensured that the flexible tube is not even partly blockingthe way of the main flow path and thus the control valve 12 is fullyopened again.

Generally, the control valve 12 can be remote controlled via thepneumatic signal activation line 18 and may be coupled to the stop cock28 such that the overpressure is applied to the control valve 12 if thestop cock 28 is positioned in the nulling position.

In one embodiment, the stop cock 28 may comprise a pivotable innermember which provides a cutting off of the fluid flow connection betweenthe reservoir 4 and the fluid flow means 24 and a connection between thefluid flow means 24 and the pressure reference depending on the positionof the inner member. The pivotable inner member is provided with a lever34 which activates the valve control element 31 in form of the bellowsuch that the bellow is squeezed and an overpressure in the pneumaticsignal activation line 18 is obtained. In other positions the lever 34releases the bellow 31 such that the pressure within the pneumaticsignal line relieves resulting in the control valve opening again.

According to other embodiments the control valve 12 can be electricallyor mechanically activated and deactivated in a remote mariner.

In the nulling position the control valve 12 is closed and the fluidflow means 24 is opened to the pressure reference such that the pressuresensor 13 can be calibrated even if the catheter tube II penetrates theblood vessel of the patient. Furthermore, the close coupling of thepressure sensor 13 with the catheter tube 11 allows for a continuousmeasuring of the blood pressure while the damping and resonance effectsare reduced.

The second interface 19 is adapted to be coupled to the operational unit3 via an appropriate plug such that an electronic monitoring unit 35 cancontinuously monitor the blood temperature and the blood pressure of thepatient.

In FIGS. 3 a to d, a preferred embodiment of the flow control unit 20 isshown. The flow control unit 20 includes a housing 50 in which a rinsingcapillary 51 included in a capillary body 59 is arranged which providesa small flow path from an upstream port 52 to a downstream port 53 ofthe flow control unit 20. The flow path has a small lumen adapted tomaintain a constant predetermined rinsing flow rate of e.g. 3 ml/h. Thefirst check valve 23 (FIG. 2) includes a first flexible member 54 afirst end of which is fixedly attached at a support element 55. A secondend of the first flexible member 54 abuts a stop area 56 of thecapillary body 59 if no additional pressure is applied. If an increasedpressure between the upstream and the downstream port 52, 53 of the flowcontrol unit 20 is applied the overpressure also acts on the firstflexible member 54 which opens if a first threshold pressure isexceeded.

The first flexible member 54 is usually closed and may be providedhaving an “umbrella behavior”, i.e. if the first threshold pressure isexceeded the first flexible member 54 flaps such that the second end ofthe first flexible member 54 is instantly removed from the stop area 56and a fluid channel is established between the upstream and thedownstream port 52, 53 of the flow control unit 20. The lumen of theestablished fluid channel has a size which allows a flow rate which isessentially larger than the rinsing flow rate through the capillary 51.

Similarly, a second check valve 22 (FIG. 2) is arranged which includes asecond flexible member 58 which is attached with a first end to thesupport element 55 and which abuts with a second end on an inner stoparea 60 of the housing 50. Therefore, the second check valve 22 isusually closed. It remains closed if a positive pressure differencebetween the upstream and the downstream port 52, 53 of the flow controlunit 20 is applied. If a positive pressure difference between thedownstream port 53 and the upstream port 52 is applied the secondflexible member 58 may flap. The second flexible member 58 is adaptedthat it flaps if a pressure between the downstream port 53 and theupstream port 52 excites a second threshold pressure. Thus, oneexemplary embodiment of a flow control unit 20 having the aforementionedfunctionality can be realized.

In FIGS. 3 b to 3 d the mechanism is illustrated for these three basicsituations. In FIG. 3 b flow through the capillary 21 takes placewhereas a threshold pressure is not exceeded.

In FIG. 3 c the situation is illustrated where the first thresholdpressure is exceeded and the first flexible member 54 flaps such thatthe second end of the first flexible member 54 is instantly removed fromthe stop area 56. This is the situation when a pressure differenceexists where the higher pressure is applied from the downstream port 53.

The other situation is illustrated in FIG. 3 d. Herein, a pressure fromthe upstream port is applied which causes a pressure difference betweenthe upstream port and the downstream port in favor of the upstream portwhich exceeds the threshold. Thus, the second flexible member 58 flapsto give way whereas the first flexible member 54 is pressed against thewall.

In FIGS. 3 e and 3 f, two situations for another embodiment of the flowcontrol unit 20 are illustrated. In this embodiment, flexible member 55in form of a ring is provided in the circumference of the housing 50.This flexible member 55 is adapted to close the lumen between thedownstream port 53 and the upstream port 52. This is accomplished byflexible member 55 being pressed against the outer wall of the memberwith capillary 21. Thus, in the situation of FIG. 3 e flow between theupstream port 52 and the downstream port 53 is only possible via thecapillary 21. In order to ensure that the flexible member 55 closes thelumen, a pressure is applied onto a medium through inlet 57. By means ofthis pressure applied, the flexible member 55 is pressed against themember comprising the capillary 21.

In FIG. 3 f a second situation is shown as in FIG. 3 e whereas nownegative pressure is applied to the inlet 57. Thus, the flexible member55 is deflated and thereby gives path for flow between the upstream port52 and the downstream port 53. The actuation of the flexible member 55to give free this path can be controlled remotely by applying therespective negative pressure. Thus, in both cases of flow from upstreamport 52 to downstream port 53 or flow from downstream port 53 toupstream port 52 the flexible member 55 can be switched from thesituation in FIG. 3 e (closed) to the situation in FIG. 3 f (open). Theopening activation signal could be derived from the nulling and samplingposition of stop cock 28.

In FIGS. 4 a and 4 b, another embodiment of the flow control unit isillustrated. The flow control unit includes a housing 70 having anupstream port 72 and a downstream port 73. Inside the housing 70 arinsing capillary 75 is arranged in a capillary body 74 to provide arinsing flow channel which is permanently opened. Neighboured to thecapillary body 74 a first flow path or channel 76 is arranged whichleads to a first check valve 77 having first flexible members 78 whichare adapted to flap if the pressure between the upstream port 72 and thedownstream port 73 exceeds a first threshold pressure. FIG. 4 a shows acondition wherein the first threshold pressure is exceeded by theapplied pressure such that the first flexible members 78 are flappedsuch that a fluid channel between the first flow path 76 and thedownstream port 73 is established.

Furthermore, a second flow path 71 is provided which leads from thedownstream port 73 to a second check valve 79 which includes secondflexible members 80 one and of which in a closed condition abut the stoparea 81 which is integrally formed with the housing 70. If a pressuredifference between the upstream port 72 and the downstream port 73exceeds a predetermined second threshold pressure the second flexiblemembers 80 flap such that the free ends of the second flexible members80 are removed from the stop area 81 such that a flow channel betweenthe second flow path 71 and the upstream port 72 is established. Thiscondition is shown in FIG. 4 b.

The first and second flexible members are preferably arranged such thatthey snap if a pressure to which they are subjected exceeds a thresholdpressure. The snapping of a valve is also known as an umbrella effect.

The first and second flexible members 78, 80 are preferably included inan integral element 81 which is formed as a flexible part and can beintroduced in the housing 70. The integral element 81 may comprise anengagement member 83 which engages in a recess 84 of the housing 70 wheninserted.

As a result, a pressure measuring system with an improved signaltransfer behavior and a simple handling is provided.

The present invention includes a disposable catheter 1 with integratedpressure sensor 13 connected to a remote disposable unit 2 (fluidtransfer unit) and a remote reusable unit 3 (operational or measurementunit). Since the catheter is usually accessible for maintenance onlywith difficulty, the necessary operations after placing the catheterlike rinsing, drawing blood samples and zeroing the pressure sensor areremotely operated. Preferred this is achieved by a preferablypneumatically operated control valve 12 and/or pressure dependent checkvalves 22, 23. For measuring and adjusting the zero point pressure aremotely controlled valve 12 is arranged before the pressure sensor 13.This is preferably a pneumatically activated stop cock or a squeezevalve. For practical reasons a hand operated shut-off valve 14 can beattached after the pressure sensor 13.

The pressure sensor 13 and the valves 12, 14 and the connector 15, arepreferably arranged in a single rigid housing at the end of the cathetertube 11 and located outside of the patient. For catheter placement thepressure sensor 13 and all firmly connected valves 12, 14 preferablypossess a straight free passage, by which a guide wire can be introducedthrough the catheter lumen 11. Frequently also a blood temperaturesensor 10 is needed. Therefore, preferably a thermistor is located atthe tip of the catheter 1 and is in thermal contact to the streamingblood of the patient. The thermistor wires (temperature sensor signallines) 16 are placed in the same catheter tube however in a separatelumen. Preferably the thermistor wires 16, the pressure transducer wires(electrical pressure signal lines) 17 and the pneumatic valve activationline 18 are connected by an interface, preferably a single plug 19 whichis integrated in the mentioned rigid housing.

Usually, such catheters need a constant small flow (3 ml/h) of a rinsingsolution. In order that this rinsing system 2 does not damp the pressuresignal, preferably immediately after the catheter connection 15 acapillary 21 is attached. Because at the same connection also bloodsamples could be taken or flush rinsing could be performed, thecapillary 21 could be bypassed dependent on the differential pressure bycheck valves 22, 23. Check valve 22 opens if the pressure in the rinsingsystem is 500 mmHg above the blood pressure in the catheter 1. Checkvalve 23 opens if the pressure in the rinsing system is 10 mmHg belowthan blood pressure in the catheter 1. The capillary 21 and the checkvalves 22, 23 are preferably arranged in a single housing 20 and thefunctions are preferably performed in a single part. In a furtherembodiment, a flexible tube 24 of appropriate length extends from thehousing 20 to a blood sample port 26, a syringe 27 and a hand operatedstop cock 28. All of them are preferably located on a bedbox at aconvenient place for the operator. The stop cock 28 is preferably at thelevel of the heart.

The stop cock 28 is preferably adapted to be placed in three positions:Rinsing position—by connecting fluid reservoir 4 to catheter 1. Nullingposition—by connecting atmosphere to catheter 1. Sampling position—byclosing all ports. Forcing stop cock 28 in nulling position preferablyalso mechanically activates a bellow 30 which activates the valve 12simultaneously via a pneumatic signal line 32.

Preferably, the interface plug 19 is connected to the sensor electronic33 by electric signal lines 25. As usual the fluid reservoir 4 is heldat 300 mmHg using a wristband.

In FIG. 5 another schematic view of one embodiment of an injectionsystem according to the present invention is shown. This view is similarto the design as shown and described in FIG. 1. In the embodiment ofFIG. 5, however, a pressure sensor 13 is provided that is connected to atube 32 filled with liquid or gel. This tube 32 has at its end areservoir 37. The other end is connected via the second interface 19 tothe blood vessel catheter unit 1. Especially, the tube 32 is connectedto a tube 36 within the blood vessel catheter unit 1. Thus, the pressureof the liquid column in tube 32 acts on the pressure sensor via tube 36.As a result, the pressure sensor is acted upon the pressure differenceof the pressure within the catheter, i.e. the patient, and the pressurewithin the column of tube 32. Tube 32 and the reservoir 37 are arrangedsuch that the reservoir is on the same height as the heart of thepatient. Thus, the pressure difference measured by the pressure sensoris the pressure within the catheter, i.e. the patient, corrected by theoffset caused by the location of the pressure sensor away from theheart. Thus, the pressure at the pressure sensor is the pressure aspresent in the patient in the heart region. In pressure sensors of theprior art, this offset has to be calculated and the read out of thepressure sensor has to be corrected mathematically to give the value ofthe pressure in the heart region. As an advantage of the presentarrangement, this pressure sensor does not have to be calibrated and setto atmospheric pressure since it already shows the correct difference,i.e. the result which is usually calculated via the absolute pressureand correction data taking into account the distance of the catheter tothe heart.

In FIG. 6, a schematic view of another embodiment of the injectionsystem according to the present invention is shown. This assembly is thesystem as described in FIG. 5 additionally providing a remote controland actuation device 40 to operate the flow control unit 20.

This arrangement is preferably used when using a flow control unit 20 asshown in FIGS. 3 e and 3 f. The opening activation signal could bederived from the nulling and sampling position of stop cock 28 which isoperating a bellow 40. Thus, it is possible to remotely control the flowcontrol unit 20 and to open the fast flush lumen or to close it. This isaccomplished similar as the activation of the valve control element 31in FIG. 1.

In FIG. 7, a more detailed schematic view of another fluid transfersystem according to the present invention is shown. This arrangement isapplicable with the system as shown in FIG. 5.

A pressure sensor 13 is arranged next to a catheter 1 having a lumen towhich the pressure sensor 13 is connected. Further, an interface 19comprising two connectors 19.1 and 19.2 being connectable to each otheris provided. The pressure sensor 13 is connected to the connector 19.1via line 36. The connector 19.2 is connected to the measurement unit 3via line 32. Line 32 includes a line filled with liquid building aliquid column, and is connected to the measurement unit 3 via a pressurechannel 111 with a hydrophobic membrane 115, and a connector 117 such asan electrical monitor circuit plug. As a result, the pressure of theliquid column within line 32 acts upon the pressure sensor via theinterface 19 and line 36.

The catheter is further connected to a rinsing and blood sample system 2by a line 24, the blood sample system 2 having a syringe 27 and a bloodsample port 26. Between catheter 1 and the rinsing and blood samplesystem 2 a flow control unit 20 is provided. This flow control unit 20includes a capillary 21 (see FIG. 1) thus allowing a rinsing of fluidfrom the fluid reservoir 4 into catheter 1. Further, the flow controlunit 20 allows for fast flush and blood sampling as described above,especially with respect to the flow control units 20 as described inFIGS. 3 a to 3 f.

When working, the measurement unit 3 will be situated at the same heightas the heart of the patient. Thus, the fluid column within line 32 willact upon the pressure sensor from the one side and the pressure withinthe lumen of catheter 1 will act upon the pressure sensor 13 from theother side. The pressure sensor 13 will then read out the difference ofthe two pressures, i.e. the pressure at the heart region of the patientas corrected by the pressure applied in line 32.

In FIGS. 8 a and 8 b, cross-sectional views from two sides of thecatheter 1 as shown in FIG. 7 are illustrated.

The catheter 1 includes a housing 95 with a catheter tube 92 arranged atthe distal end of the housing 95 comprising an inner lumen 93. Thecatheter tube 92 is connected to the housing via a bend protection 96.At the proximal end of the housing, a luer access 124 is provided.

In the housing 95 a pressure sensor 13 is arranged next to a pressurechannel 99 (which is filled with liquid) extending from the inner lumen93. The pressure sensor 13 is connected to the pressure channel 99 via atransmission membrane 100, preferably made of gel. On the other side,the pressure sensor is connected to a pressure channel 101. The pressurechannel 101 is attached to a strain relief 105. Within the strain relief105, other circuits like the pressure channel 101, a connection cable102 and electrical circuits 106 are integrated. The pressure channel 101is filled with a pressure transmitting material, for instance gel orwater emulsions. Within the housing 95 further sensors 107 like atemperature sensor is integrated.

With such an arrangement, the pressure sensor 13 is subjected to apressure difference between the pressure in the pressure channel 99 andthe pressure from pressure channel 101 acting upon the pressure sensor13.

Further, the pressure sensor is kept out of the way of the inner lumen.Thus, a guide wire to be inserted into the inner lumen can not bebrought into contact with the pressure sensor and damage the pressuresensor. It is advantageous to choose the angle of the pressure channel99 within the housing in such a way that the housing 95 additionallyprotects the catheter tube 92 from damages by bending. Further, thehousing 95 provides for an advantage distance between the luer access124 from the skin of the patient. Preferably, the housing 95 includes abase plate 91 that can be placed on the skin of the patient. Incombination with a bend protection 96 which itself is preferablybendable, a good protection for the catheter tube 92 is provided.

In FIG. 8 b a view onto catheter 1 is illustrated. At the distal end ofthe catheter tube 92, a conical formed tip 94 is provided. The housingfurther includes suture eyes 97.1 and 97.2 for fastening the housing tothe skin of the patient.

In FIG. 9 a more detailed view of the interface 19 as shown in FIG. 7 isillustrated.

The interface 19 includes two connectors 19.1 and 19.2. The connector19.1 is connected to the blood vessel catheter unit 1 whereas theconnector 19.2 is connected to the measurement unit 3. A connectioncable 102 coming from the catheter unit 1 includes different circuitsand a pressure channel 101 coming from the pressure sensor 13 asindicated in FIG. 8 a. The interface connector 19.1 is made as a plugmatching to the counter part interface connector 19.2. The pressurechannel 101 forms a puncture spike 104 within the first interfaceconnector 19.1. This puncture spike is preferably made of a thin,bendable tube out of Nitinol. At the other side, a puncture membrane 114is provided. This puncture membrane closes a water column 110 towardsthe second interface connector 19.2. This puncture membrane can be madeof elastic material, for instance silicon discs, already comprising apuncture which is long enough to prevent water to flow through the longpuncture within the elastic material. Thus, no water from the watercolumn 110 can flow out. In the upper part of the second connector 19.2,the electrical circuits 109 are provided around the water column 110within the monitor cable 108.

When the two connectors 19.1 and 19.2 are put together, the electricalcircuits of the connectors 19.1 and 19.2 will be plugged together.Further, the puncture spike 14 will penetrate the puncture membrane 114thus giving way between the fluid medium, preferably gel, of thepressure channel 101 and the water column 110. Since within the puncturemembrane 114 there was already provided a puncture, the puncturemembrane is not inflicted. Thus, when separating the two connectors 19.1and 19.2 from each other again, the puncture membrane 114 will againclose the water column 110.

The other end of the water column 110 is either open or protected by ahydrophobe membrane 115 (FIG. 7) which is permeable to air and notpermeable to water to avoid loss of water. This other end of the watercolumn 110 is situated at the height of the heart. Thus, the pressuresensor will output the correct difference of pressure with respect tothe location of the heart. Preferably, the inner diameter of the watercolumns 110 is chosen so small that the water is additionally hinderedto flow out because of these dimensions. The other end of the watercolumn can be fixed at the height of the heart by integrating the watercolumn 110 within the monitor cable 108 or an electrical monitor circuitplug which is connectable to a so called monitor-bed-box. On the frontplate or panel of this monitor-bed-box, further system members likeblood sampling ports, etc. can be mounted. Preferably, the other openend of the water column 110 end into a clamping piece on the monitorcable 108 between the electrical circuits and can be fixed at a suitablelocation at the height of the heart. Further, additional clamping piecescan be provided on the monitor cable 108 to allow fasten a rinsingconduit.

To the luer access 124 of the housing 95 a capillary valve or a flowcontrol unit, for instance according to FIGS. 3 a to f, with a rinsingconduit or capillary can be connected. Thus, a continuous rinsing ofcatheter 1 is achieved and at the same time a decoupling of the rinsingconduit that is tampering with the accuracy of the measuring signals andthe blood sample units from the pressure channel is achieved.

What is claimed is:
 1. A blood vessel catheter system, comprising: acatheter tube having a first portion configured for insertion into ablood vessel of a patient, and a second portion configured to remainoutside the body of the patient when the first end is inside the bloodvessel; a pressure sensor configured for connection outside of thepatient's body to the second portion of the catheter tube, wherein thepressure sensor is configured to sense pressure in a liquid inside thecatheter tube as an indication of a blood pressure of the patient,wherein the pressure sensor is configured to generate an electricpressure signal indicative of the blood pressure, and wherein thepressure sensor includes an electric interface configured to releasablycouple the pressure sensor to a reusable measurement unit; a reservoirof rinsing fluid connected to the second portion of the catheter tube; astop cock connected to the second portion of the catheter tube andconfigured for selective placement into at least: a rinsing position inwhich the stop cock allows a flow of rinsing fluid from the reservoir tothe second portion of the catheter tube; a nulling position in which thestop cock establishes the application of a predetermined referencepressure to the pressure sensor, and a sampling position in which thestop cock prevents the flow of rinsing fluid from the reservoir to thesecond portion of the catheter tube; and a flow control unit positionedbetween the reservoir and the second portion of the catheter tube, saidflow control unit comprising: an upstream end in fluid communicationwith the reservoir; a downstream end in fluid communication the secondportion of the catheter tube; and structure between the upstream end andthe downstream end of the flow control unit defining first, second, andthird fluid flow paths between the reservoir and the second portion ofthe catheter tube: wherein said first fluid flow path includes anon-closing rinsing capillary configured to permanently allow fluidcommunication between the upstream end and the downstream end of theflow control unit, and a controlled flow of fluid between the reservoirand the second portion of the catheter tube when the stop cock is in itsrinsing position; wherein said second fluid flow path includes a firstcheck valve configured to open when fluid pressure at the downstream endof the flow control unit exceeds a fluid pressure at the upstream end ofthe flow control unit by a first predetermined threshold pressuredifference; and wherein said third fluid flow path includes a secondcheck valve configured to open when fluid pressure at the upstream endof the flow control unit exceeds fluid pressure at the downstream end ofthe flow control unit by a second predetermined threshold pressuredifference.
 2. The blood vessel catheter system of claim 1, wherein saidsecond predetermined threshold pressure difference is greater than saidfirst predetermined threshold pressure difference.